Furniture plates are usually metal rectangular plate members which are attached to each side of a door and in the area where the lock/handle is attached to the door. The plates typically have a thickness of between 1-30 mm, a length of typically between 5-20 cm, and a width of typically between 3-10 cm. The plates are usually screwed in position by either wood screws or metal thread screws. Metal thread screws are generally preferred because in most cases they provide a more secure form of attachment. The plates can improve the security of the door lock by making it more difficult to punch a hole through the door to access or to vandalise the lock components.
If a high degree of security is required, there is an advantage in being able to attach the furniture plates in a concealed manner which means that the attachment screws are not visible or cannot be manipulated by an intruder. A concealed attachment can also provide an aesthetic arrangement to the door.
It is known to provide a concealed screw system involving the use of screws which are accessed through an edge rather than the front face of the furniture plate. While this provides a level of deterrent to an intruder, the arrangement is not entirely satisfactory in practice because the screw heads are still accessible to a degree sufficient to permit intrusion. The system is not entirely satisfactory for aesthetic reasons because of the need for recesses in the plate edge to receive the screw heads.
It is known to provide a concealed fastening arrangement which includes at least one tension member secured to an inside surface of the furniture plate and which extends substantially at right angles from the inside surface of the furniture plate, the tension member being located within the body of the door, and a camming member located in the door body and which engages with the tension member to pull the tension members together thereby pulling the furniture plates against the door side surfaces. A camming arrangement has disadvantages including the lack of fine adjustment and the need to have precisely machined and positioned components to ensure proper engagement of the cams.